Norwich Public Utilities’ planned $8 million natural gas expansion is expected to bring at least $250,000 to city coffers once the project is complete, a company official said Saturday.

“More than likely it will be more, but we’re conservative with that and make sure we have the numbers as right as we can get them,” NPU spokesman Mike Hughes said during an informational session sponsored by the Greater Norwich Area Chamber of Commerce on the company’s bond referendum that will appear on November’s ballot.

Norwich’s charter requires NPU to direct 10 percent of its yearly revenue to the city. The utility expects to make about $2.5 million per year from the expansion.

The measure, if approved, will allow NPU to lay down natural gas lines in more than dozen neighborhoods across the city. The utility says there must be enough customers signing up for new gas service in an area to guarantee repayment of construction.

It’s a funding mechanism that protects residents not hooked onto natural gas lines from paying for any of the work, Hughes said.

Susie Forbes, who moved to Norwich a year from Gales Ferry, said she supports NPU’s plan and believes the cost savings will be significant.

“I haven’t hears a bad thing about it. Having to live with oil is not my thing,” she said. “I would invest in natural gas because it burns cleaner and heats cleaner.”

Hughes said the decision to bond for more gas lines comes from the “widely successful” results of a November 2010 vote by city resident that authorized $3 million for an initial network of pipelines that has reached more than 500 dwellings to date.

The benefit for businesses is also tangible, said Bob Mills, executive director of Norwich Community Development Corp.

“If you’re in business and have to sell so much product or do so much work to cover your costs, taking 10 or 12 percent out of that is $10 less revenue required for that dollar of cost,” he said.